nodetool netstats – Prints network information about the host.
The output includes the following information:
- JVM settings
- Mode – The operational mode of the node: JOINING, LEAVING, NORMAL, DECOMMISSIONED, CLIENT
- Read repair statistics
- Attempted – The number of successfully completed read repair operations.
- Mismatch (blocking) – The number of read repair operations since server restart that blocked a query.
- Mismatch (background) – The number of read repair operations since server restart performed in the background.
- Pool name – Information about client read and write requests by thread pool size.
- Active, pending, and completed number of commands and responses
“Streaming” is a component which handles data (part of SSTable file) exchange among nodes in the cluster.
When you bootstrap a new node, it gets data from existing nodes using streaming. When you run
nodetool repair, nodes exchange out-of-sync data using streaming.
we can get the stream id from system.log(/var/log/cassandra/system.log) by grep for the keyword ‘stream’
$ ps -ef|grep -i stream
$ grep -i stream system.log|head
INFO [RepairJobTask:2] 2019-07-31 07:17:58,717 StreamResultFuture.java:93 - [Stream #d9f1d3b0-b384-11e9-9c0e-b71e006e5d73] Executing streaming plan for Repair
INFO [RepairJobTask:1] 2019-07-31 07:17:58,742 LocalSyncTask.java:103 - [repair #d9639d70-b384-11e9-9c0e-b71e006e5d73] Performing streaming repair of 5 ranges to and 0 ranges from/220.127.116.11
The same way we can get the details like when a stream is started and when it is ended by grep for the keyword ‘Stream’ from system.log as follows :
# grep -i stream system.log|head
INFO [RepairJobTask:1] 2019-07-31 07:17:58,744 StreamResultFuture.java:93 - [Stream #da15af60-b384-11e9-9c0e-b71e006e5d73] Executing streaming plan for Repair
INFO [StreamConnectionEstablisher:2] 2019-07-31 07:17:58,745 StreamSession.java:281 - [Stream #da15af60-b384-11e9-9c0e-b71e006e5d73] Starting streaming to /127.0.0.1
# grep -i stream system.log|tail
INFO [StreamReceiveTask:3] 2019-08-16 07:29:49,222 StreamResultFuture.java:233 -
[Stream #27f788c0-c019-11e9-9c0e-b71e006e5d73] All sessions completed
INFO [StreamReceiveTask:3] 2019-08-16 07:29:49,222 LocalSyncTask.java:138 - [repair #27ce2ed0-c019-11e9-9c0e-b71e006e5d73]
Sync complete using session 27ce2ed0-c019-11e9-9c0e-b71e006e5d73
between /127.0.0.1 and /127.0.0.2 on repair_history